What is the Gradle Wrapper (gradlew)?

The Gradle Wrapper is a small set of files committed with a project (gradlew, gradlew.bat and gradle/wrapper/) that runs the build with a specific Gradle version. The first time you run ./gradlew build, it downloads that version into ~/.gradle/wrapper/dists/ and then uses it; later runs reuse the download. Nobody needs Gradle installed, and every developer and CI job builds with the same version.

The files

Commit all four. The version lives in distributionUrl:

distributionUrl=https\://services.gradle.org/distributions/gradle-X.Y-bin.zip

(X.Y stands for the Gradle version of the project.)

Use it

./gradlew build          # Linux, macOS (Git Bash too)
gradlew.bat build        # Windows cmd / PowerShell: .\gradlew.bat build
./gradlew --version      # Gradle version the wrapper uses

If ./gradlew fails with Permission denied on Linux or macOS, the execute bit was lost (common after a checkout from Windows): run chmod +x gradlew and commit it with git update-index --chmod=+x gradlew.

Upgrade the Gradle version

./gradlew wrapper --gradle-version X.Y    # rewrites the properties file and scripts
./gradlew wrapper                         # run again so the new version updates the wrapper JAR too

Run it twice as shown: the first run uses the old Gradle to write the new version; the second runs with the new version and refreshes the wrapper files themselves. Commit the changed files.